The present invention is directed to ink compositions, and more specifically, the present invention relates to inks especially useful for acoustic ink printing, processes and apparatuses thereof, reference for example, the above recited copending patent applications, and U.S. Pat. No. 5,121,141, U.S. Pat. No. 5,111,220, U.S. Pat. No. 5,128,726, U.S. Pat. No. 5,371,53, U.S. Pat. No. 5,528,384 and U.S. Ser. No. 176,381, now abandoned the disclosures of which are totally incorporated herein by reference, including especially acoustic ink processes as illustrated in some of the aforementioned copending applications and patents, such as an acoustic ink printer for printing images on a record medium. Also, the inks of the present invention may be useful as ink jet inks, and for thermal ink jet processes.
More specifically, the present invention is directed to hot melt acoustic ink compositions wherein there can be generated with such inks excellent developed images with acceptable image permanence, excellent projection efficiency on transparencies without a post fusing step, and excellent crease resistance, and wherein the inks possess acceptable, and in embodiments superior lightfastness, and superior waterfastness. Moreover, in embodiments of the present invention, there are provided inks that enable the elimination, or minimization of undesirable paper curl since water is not usually present, however, very small amounts of water can be selected in embodiments. With the inks of the present invention, it is preferred that there be an absence of water, and since water is not present in the inks a dryer can be avoided thereby minimizing the cost of the acoustic ink jet apparatus and processes thereof. Moreover, the absence of water permits the use of the inks in high volume printers and wherein the concerns about humidity, especially humidity increases, and the removal of water are avoided. The inks of the present invention in embodiments thereof are comprised of a colored vehicle and optionally a noncolored vehicle, reference U.S. Pat. Nos. 5,688,312; 5,667,568; 5,700,316 and 5,747,554, the disclosures of each application being incorporated herein by reference; and more specifically, wherein the invention ink resin is comprised of a reversibly crosslinked polymer based on the reversible cycloaddition reaction between a furan and a maleimide, which products have a low degree of coupling at higher temperatures, for example from about 100 to about 180.degree. C., and a high degree of coupling at lower temperature, for example from about 10 to about 40.degree. C. Coupling refers, for example, to the reaction of pendant or terminal groups on one chain with groups on another second chain to effect an increase in molecular weight. Reversibility indicates, for example, that the amount of coupling achievable after an extended time period, that is for example, the equilibrium amount of coupling, or an extended time period of from a few hours to several months, and preferably from about 3 hours to about 24 hours, and the coupling is primarily affected by the temperature, thus the degree of coupling can be increased or decreased by decreasing or increasing the temperature, respectively, through several temperature cycles, with substantially the same results on each cycle, which is of importance since, for example, a number of ink components can experience, in the AIP print head, several heating and cooling cycles corresponding to the off and on behavior of the printer, and it is desirable that such a history not have a significant adverse effect on the performance of the ink.